Convert iris.analysis.SUM to a weighted aggregator. Closes #595.
grib hind doc
Merge pull request #547 from bblay/hinddoc

Improve documentation of GRIB hindcast workaround flag.
Merge pull request #626 from ajdawson/weighted-sum

Convert iris.analysis.SUM to a weighted aggregator.
Merge pull request #629 from rhattersley/pep8-iris.quickplot

PEP 8 iris.quickplot
PEP 8 iris.coord_categorisation